Coordinated medium voltage therapy for improving effectiveness of defibrillation therapy

ABSTRACT

Automated treatment of arrhythmia utilizing an electrotherapy device. Time-coordinated applications of medium-voltage therapy (MVT) followed by high-voltage therapy (HVT) include a first MVT waveform to a first target region and a second MVT waveform to a second target region, such that the HVT is synchronized relative to a first compression cycle corresponding to activation of the first target region, and to a second compression cycle corresponding to activation of the second target region resulting from the administration of the MVT.

FIELD OF THE INVENTION

The invention relates generally to electrical treatment for individualsexperiencing cardiac arrest and, more particularly, to implantable orexternal treatment apparatus and associated methods of operationthereof, for improving the effectiveness of defibrillation treatmentutilizing coordinated administration of medium voltage therapy (MVT).

BACKGROUND OF THE INVENTION

Cardiac arrest is a significant public health problem cutting acrossage, race, and gender. A positive impact on cardiac arrest survival hasbeen demonstrated with the substantial reduction in time todefibrillation provided by the widespread deployment of automatedexternal defibrillators (AEDs), and the use of implantable cardioverterdefibrillators (ICDs) and implantable pulse generators (IPGs). Examplesof AEDs are described in U.S. Pat. Nos. 5,607,454, 5,700,281 and6,577,102; examples of ICDs are described in U.S. Pat. Nos. 5,391,186,7,383,085, and 4,407,288, and examples of IPGs are described in U.S.Pat. Nos. 4,463,760, 3,978,865, and 4,301,804, the disclosures of whichare incorporated by reference herein.

Optimal resuscitation therapy for out of hospital (OOH) cardiac arrestis the subject of substantial ongoing research. Research has been clearin demonstrating that the timing of resuscitation is of criticalimportance. For example, there is less than a 10% chance of recoveryjust ten minutes after the onset of ventricular fibrillation (VF). Thisknowledge led to the recent widespread deployment of AEDs, primarily inpublic areas with a high population concentration such as airports andshopping malls. A positive impact on cardiac arrest survival has beendemonstrated due to the substantial reduction in time to defibrillationas a result of more available access to AEDs. In addition, for thosepatients identified as being at particularly high risk, an implantablecardioverter-defibrillator is often implanted in order to addressepisodes of cardiac arrest without the involvement of a rescuer.

In the case of VF, performing CPR-type chest compressions beforedefibrillation or between successive defibrillation shocks andminimizing the time to defibrillation shock following the cessation ofthe CPR chest compressions is important in facilitating effectiverecovery especially in cases of long duration VF. It is generallybelieved that perfusion of the myocardium achieved during CPRpreconditions the heart for the defibrillating shock. Despite theimportance of CPR, it is often not performed in the field for a varietyof reasons.

MVT has also been recognized as a way of forcing some amount of cardiacoutput by electrically stimulating muscle tissue directly with stimulithat cause the heart or skeletal muscles to contract in a controlledcycle. See U.S. Pat. Nos. 5,735,876, 5,782,883 and 5,871,510. Thesepatents describe implantable devices having combined defibrillation, andMVT capability for forcing cardiac output. U.S. Pat. No. 6,314,319describes internal and external systems and associated methods ofutilizing MVT to achieve a hemodynamic effect in the heart as part of animplantable cardioverter defibrillator (ICD) for purposes of achieving asmaller prophylactic device. The approach described in the '319 patentuses the MVT therapy to provide a smaller and less expensive implantabledevice that can maintain some cardiac output without necessarilyproviding defibrillation therapy.

Unlike a conventional defibrillator, which operates with the primarypurpose of restoring a normal cardiac rhythm, or an IPG that operates tocontrol the rate of an existing cardiac rhythm, MVT stimulation can beused to provide cardiac output, which in turn causes perfusion to theheart and brain, as well as other critical body tissues. By providingperfusion to the heart and other vital organs, MVT prolongs the life ofthe patient even while the patient continues experiencing thearrhythmia. Additionally, MVT improves the likelihood of successfuldefibrillation or of a spontaneous return of circulation. An AEDequipped with MVT can provide consistent high quality chestcompressions. In the case of an implanted ICD or IPG, back up chestcompressions provided by MVT can, in one sense, be even more importantthan in an external, since in the case of the implantable device theremay be no rescuer available to perform CPR when needed.

U.S. Patent Application Publication No. 2006/0142809, the disclosure ofwhich is incorporated by reference herein, describes a technique andassociated apparatus that combines defibrillation therapy with MVT intoan external device having a capability to perform electrical CPR.Externally-applied MVT is proposed for stimulating skeletal andsympathetic muscles in addition to myocardial muscle tissue to effectchest compression and even ventilation in the patient. The '809publication reflects the knowledge in the art that due to the inclusionof differing time constant components in an MVT waveform, the waveformcan stimulate contraction of a variety of different types of muscles,e.g., myocardial, skeletal, sympathetic muscles, and the phrenic nerve.Varying and controlling the MVT waveform parameters, including variationof the musculature targeted by the waveform, is described as a way tomaximize coronary perfusion pressure generated by application of MVT.

Separately, there have been developments in automated chest compressiondevices that apply mechanical pressure in repeated CPR-like cycles to apatient's chest area. These devices may incorporate defibrillationtherapy as well, such as disclosed in U.S. Pat. No. 6,398,744. Althoughmechanical chest compression devices are useful in situations wheresustained manual CPR is difficult or tiring for rescuers, such as inlengthy ambulance trips or airlifts, for example, these devices includea belt that must be positioned around a patient's chest, making themgenerally unsuitable for use by layperson rescuers. There is also noimplantable analogous device that could apply mechanical chestcompressions.

More recently, a mechanical chest compression device has been used tostudy the effects of delivering defibrillation therapy at various pointsin the chest compression cycle. U.S. Pub. No. 2009/0149903 discloses theresults of animal research in which the mechanical chest compressioncycle of a porcine model was measured directly using a load cell forcetransducer, the output of which was used to control the time ofapplication of the defibrillation energy. The empirical results of thiswork suggest that application of the defibrillation therapy at the endupstroke phase of the compression cycle produced an increased successrate of converting the ventricular fibrillation.

It would be desirable to apply some of these chest compressioncycle-defibrillation synchronization principles learned from mechanicalchest compression technology to devices utilizing MVT to take advantageof the ease of use of AED devices requiring only the placement ofelectrodes, plus the ability to implement compressioncycle-defibrillation synchronization in implantable devices. Previously,it has been proposed to time a defibrillation shock after a skeletalmuscle stimulating pre-shock waveform for an implanted subcutaneousdevice, as disclosed in U.S. Pub. No. 2004/00220628. This approachattempts to compress the thorax to reduce conduction path length for thesubsequent defibrillation shock, thereby reducing the defibrillationshock impedance and concentrating the defibrillation current to theheart.

Synchronizing electrically-stimulated chest or heart compressions withdefibrillation therapy presents its own set of challenges. Although thedefibrillation pulses can be precisely timed relative to the start orcessation of the muscle stimulation by triggering the discharge ofappropriate waveforms and energy at the appropriate times, synchronizingthe defibrillation pulses to the chest compressions themselves is not sostraight-forward to control. For instance, each individual patient has aparticular size, chest cavity structure, lung volume, skeletal musclemass, muscle tone, heart volume and mass, etc. These all factor into thecharacteristics of the compression cycle that can be produced byapplying MVT, and vary patient-to-patient. Likewise, the particularpatient's disease state or symptoms thereof, such as cardiomegaly, i.e.,enlarged heart, for example, can affect the timing and quality of thecompression cycle induced by MVT administration. Moreover, electricalmuscle stimulation approaches cannot directly measure the compressioncycle using the type of load cell sensor disclosed in the 2009/0149903publication.

The 2004/00220628 publication recognizes some of these challenges andproposes that the time delay between the pre-shock waveform and thedefibrillation shock be varied patient-to-patient or shock-to-shock.However, this reference does not address how the time delay is to bevaried, or what the basis for varying the time delay should be.Moreover, it is not apparent from the art whether the seeminglycontradictory teachings of the 2004/00220628 publication emphasizingapplying the defibrillation shock at the point where the chest is mostcompressed, can be reconciled with the findings of U.S. Pub. No.2009/014990 suggesting the optimal point of defibrillation shockdelivery should be when the chest has rebounded after a chestcompression.

Optimal arrhythmia treatment continues to be a subject of ongoingresearch and development. In spite of the substantial progress in theresearch to understand the underlying biological mechanisms inelectrical conversion of arrhythmias, a complete understanding (beyondhere hypotheses) of the effects of all of the associated parameters,such as the effect of chest compressions, has been elusive. Thereremains a need for further improvement of treatment apparatus andassociated processes to increase the effectiveness of these life-savingtherapies.

SUMMARY OF THE INVENTION

One aspect of the invention is directed to automated treatment ofarrhythmia utilizing an electrotherapy device. Time-coordinatedapplications of medium-voltage therapy (MVT) followed by high-voltagetherapy (HVT) are administered as a time-coordinated sequence. Thesequence includes a first MVT waveform to a first target region and asecond MVT waveform to a second target region, such that the HVT issynchronized relative to a first compression cycle corresponding toactivation of the first target region, and to a second compression cyclecorresponding to activation of the second target region resulting fromthe administration of the MVT.

In a related aspect, an electrotherapy device for treating arrhythmia ina patient includes a patient interface, patient monitoring circuitry,electrotherapy circuitry, and a controller circuit.

The patient interface includes a plurality of electrodes, each having asurface that facilitates electrical contact with the patient. Theelectrotherapy circuitry is operatively coupled to the patient interfaceand includes a medium voltage therapy (MVT) circuit operatively coupledto the patient interface and constructed to administer MVT via thepatient interface to each of a plurality of target regions of thepatient. The MVT has an insufficient energy level to shock the heartinto a reset state, but having an energy level and a variable waveformthat causes musculature in each corresponding target region to be (a)electrically activated into a contracted state, (b) electricallymaintained in the contracted state for a compression duration, and (c)thereafter allowed to relax, thereby achieving a forced compression andrelease of that target region. The plurality of target regions includesa first target region having primarily skeletal musculature, and asecond target region having primarily myocardial musculature. A highvoltage therapy (HVT) circuit is operatively coupled to the patientinterface and constructed to supply the HVT via the patient interface.The HVT is of an energy level sufficient to shock the heart into a resetstate.

The patient monitoring circuitry includes an arrhythmia monitoringcircuit operatively coupled to the patient interface and configured tomeasure indicia of an arrhythmia treatable by the HVT.

The controller circuit is operatively coupled to the patient monitoringcircuitry and the electrotherapy circuitry, and includes MVTadministration logic configured to cause the electrotherapy circuitry toadminister the MVT as a series of repeated, time-coordinated,applications of MVT waveforms to the first and the second targetregions, respectively, in response to a detection of a presence of anarrhythmia treatable by the HVT based on an output of the patientmonitoring circuitry. Also, the controller includes HVT administrationlogic configured to cause the electrotherapy circuitry to administer theHVT in response to the detection of the presence of the arrhythmiatreatable by the HVT, and in time-coordinated response to a sequence ofthe time-coordinated applications of the MVT that includes a first MVTwaveform to the first target region and a second MVT waveform to thesecond target region, such that the HVT is synchronized relative to (a)a first compression cycle corresponding to activation of the firsttarget region, and (b) a second compression cycle corresponding toactivation of the second target region, resulting from theadministration of the MVT.

A number of advantages will become apparent from the following DetailedDescription of the Preferred Embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating the sub-systems of an implantabledevice enabled with medium voltage therapy (MVT) facilities, accordingto one embodiment.

FIGS. 2A-2C illustrate various examples of electrode arrangements forimplantable MVT devices such as the device of FIG. 1 according tovarious embodiments.

FIG. 3A is a diagram illustrating the sub-systems of an external deviceenabled with medium voltage therapy facilities, according to oneembodiment.

FIG. 3B is a diagram illustrating an exemplary operator interface of thedevice of FIG. 3A.

FIG. 3C is a diagram illustrating various examples of electrodes andsensors of the patient interface of the device of FIG. 3A.

FIGS. 4A-4B are time-domain waveform diagrams illustrating variableparameters of the MVT according to various embodiments of the invention.

FIGS. 5A-5B are timing and flow diagrams, respectively, that depict anexemplary time-coordinated treatment sequence involving two types oftargeted MVT stimulation synchronized with defibrillation therapyaccording to one embodiment.

FIG. 6 is a flow diagram representing an exemplary process of adaptingMVT or timing parameters in response to chest compression phase andhemodynamic monitoring according to one embodiment.

FIG. 7 is a flow diagram illustrating an exemplary rescue process inwhich an electrotherapy device utilizes MVT in sustain mode, and MVT inpre-defibrillation mode, according to one type of embodiment.

FIG. 8 is a block diagram illustrating some of the logic modulesimplemented in a controller of an electrotherapy device according to oneembodiment.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram illustrating an implantable electrotherapydevice 10 constructed in accordance with one aspect of the invention.The device circuitry is electrically coupled with regions of thepatient's upper body 40 via a series of leads—output lead 32, pressuresense lead 34, and ECG sense lead 36. The electronic circuit includes aconventional ECG amplifier 30 for amplifying cardiac signals. Theamplified cardiac signals are analyzed by a conventional arrhythmiadetector 20 which determines if an arrhythmia is present. The arrhythmiadetector 20 may be one of several types well known to those skilled inthe art and is preferably able to distinguish between different types ofarrhythmias. For example; fibrillation, tachycardia, asystole.

The exemplary circuit also contains a hemodynamic sensing section 28which amplifies and conditions a signal from a one or more hemodynamicsensors such as, for example, a pressure sensor within the heart orartery, such as the pressure sensor described in U.S. Pat. No.6,171,252, the disclosure of which is incorporated by reference herein.Another type of hemodynamic sensor that can be used in an implantableembodiment is a microphone and associated processing device formonitoring audible body sounds (much like an indwelling stethoscope)indicative of blood flow as described in U.S. Pat. No. 7,035,684, thedisclosure of which is incorporated by reference herein. Yet anothersuitable hemodynamic sensing technique is one featuring an ultrasonicblood flow sensor, such as the Doppler pulse sensor described in U.S.Pat. No. 4,823,800, the disclosure of which is incorporated by referenceherein. Still another hemodynamic sensing technique that may be employedis impedance plethysmography (tomography) in which a series ofelectrodes are placed to measure changing impedance in localized regionsindicative of blood flow, a pulse, or movement of the cardiac wall suchas described in U.S. Pat. No. 5,824,029, the disclosure of which isincorporated by reference herein. A further technique of measuring thehemodynamic output of the patient is with the use of a pulse oximetersuch as the implantable one described in U.S. Pat. No. 4,623,248, thedisclosure of which is incorporated by reference herein.

The output of the hemodynamic sense circuit 28 is fed to a cardiacoutput detection circuit 18 which analyzes the data and determines anestimate of the cardiac output. Data from the arrhythmia detectorcircuit 20 and the cardiac output detection circuit 18 is fed to thecontroller 16. The controller 16 determines if electrotherapy, such asdefibrillation or MVT, is appropriate, and what electrotherapyparameters to apply at the present time. If defibrillation or MVT isindicated, the controller 16 prompts the output control 22 to charge acapacitor within the output circuit 26 via the capacitor charger 24. Theoutput control 22 directs the output circuitry 26 to deliver the pulsesto the patient's upper body regions 40 via the output leads 32. Thecontroller 16 may communicate with external sources via a telemetrycircuit 14 within the device 10. The power for the device 10 is suppliedby an internal battery 12.

FIG. 2A is a diagram showing the connection of an implantabledefibrillation device 10′ according to one embodiment to the heart asone of the regions in the patient's upper body 40 in an epicardial patchconfiguration. In this thoracotomy configuration, current passes throughan output lead pair 32 to electrode patches 42 which direct the currentthrough the heart. A pressure sense lead 34 passes the signal from anoptional pressure transducer 46 which lies in the heart. The ECG ismonitored by sense electrodes 44 and passed to the device 10′ by a lead36. The area of the electrodes 42 is at least 0.5 cm². The size of theelectrode is greater than that of a pacing lead, or betweenapproximately 0.5 cm² and 20 cm² each.

FIG. 2B illustrates an example of a non-thoracotomy arrangementaccording to one embodiment. In this system, the current passes from acoil electrode 52 in the heart to the housing of the MVT device 10″. Anendocardial lead 50 combines the ECG sensing lead and the pulse outputlead. The ECG is monitored by sense electrodes 44 in the heart andpasses through the endocardial lead 50. There is an optional pressuretransducer 46 in the heart which passes a signal to the device 10″ viaoptional lead 34.

FIG. 2C illustrates an implantable electrotherapy device 10″′ thatsupports a set of diverse electrode arrangements for selectivelyapplying defibrillation, as well as MVT, to different areas of thepatient. In addition to electrodes 42 and 52 discussed above in thethoracotomy and non-thoracotomy arrangements for directing the MVTthrough the myocardium, device 10″′ further includes additionalelectrodes 58 a and 58 b for placement at specific locations in thepatient's upper body, 60 a and 60 b, to direct MVT through non-cardiacmuscles. Examples of locations 60 a and 60 b include (withoutlimitation) locations for activating the pectorial muscles, intercostalsmuscles, the diaphragm (e.g., via stimulation of the phrenic nerve), andthe abdominal muscles. The additional electrodes 58 a and 58 b, invarious embodiments, have a variety of constructions and locations,including, for example, subcutaneous patch electrodes, one or moreadditional electronics/battery housings, intra-vascular leads, and thelike. Placements include any suitable location such as, for example,subcutaneously at the base of the neck, in the azygos vein, in thecephalic vein, subcutaneously in the lower torso, and subcutaneously onone or both sides of the upper torso.

In a related embodiment, the additional one or more of electrodes 58 aand 58 b are used for hemodynamic measurements such as, for example,electrical impedance plethysmography or tomography. In one suchembodiment, one of the additional electrodes 58 a, for instance, isimplanted high in the upper chest region or at the base of the neck,while another one of the additional electrodes, 59 a, for instance, isimplanted lower in the abdominal region. Even though electrode 58 a andelectrode 59 a may not used as a cathode/anode pair for application ofMVT (this would be the case where, for example, electrode 58 a has acomplementary electrode 58 a placed elsewhere for applying MVT to region60 a, and where electrode 59 a has a complementary electrode 59 a placedelsewhere for applying MVT to region 60 b), one of electrodes 58 a andone of electrodes 59 a can be operated as an anode/cathode pair witheach other for purposes of impedance measurement to determine bloodflow, using a suitable switching arrangement in the implantable MVTdevice 10′.

In a related embodiment, an electrical impedance measurement isperformed using frequency division or code division multiplexingrelative to applied MVT therapy. Thus, the impedance measurement may becarried out while rejecting the interference caused by application ofthe MVT signals. This approach permits a hemodynamic impedancemeasurement to be performed without having to interrupt application ofthe MVT and without having to time the measurement to coincide with timeperiods between MVT pulse packets. Accordingly, in one embodiment, areal-time, continuous hemodynamic monitoring is performed while MVT isadministered. The blood flow can thus be plotted as a function of time,and correlated to the parameters of the MVT being applied. Thisinformation can be displayed to an operator as a chart recording ordisplayed trace, and can be automatically stored and analyzed toascertain MVT performance.

FIG. 3A is a diagram illustrating an example AED 100 that utilizes MVTaccording to one embodiment. AED 100 can be a hand-portable instrumentthat is self-powered from an optionally-rechargeable battery 102.Battery 102 provides an energy source that can be converted andconditioned for powering the various circuitry of AED 100. A low voltagepower supply 104 converts the battery power into one or more stabilizedpower supply outputs 105 for supplying the power to the subsystems ofAED 100. The subsystems include a controller 106, for example amicroprocessor that is programmed and interfaced with other subsystemsto control most of the functionality of AED 100.

In the embodiments in which the controller 106 is implemented as amicroprocessor or microcontroller, the microprocessor interface includesdata and address busses, optional analog and/or digital inputs, andoptional control inputs/outputs, collectively indicated atmicroprocessor interface 107. In one example embodiment, themicroprocessor is programmed to control the sequence of theelectrotherapy, as well as the output waveform parameters. The userinput to the system can be in the form of simple pushbutton commands, orvoice commands.

Example AED 100 includes a discharge circuit 108 for administeringtherapeutic stimuli to the patient. Discharge circuit 108 controls therelease of therapeutic energy to achieve a desired stimulus having aparticular waveform and energy. Charge circuit 110 energizes dischargecircuit 108 to achieve the desired output stimulus. High voltage powersupply 112 provides a sufficient energy source 113 to charge circuit 110to enable charge circuit 110 and discharge circuit 108 to ultimatelydeliver one or more defibrillation pulses to an exterior surface of thepatient. Typically, a voltage sufficient to achieve a therapeuticdefibrillation stimulus from the exterior of a patient is in the rangeof 1 kV-3 kV.

In accordance with this embodiment, AED 100 also includes a mediumvoltage power supply 114. Medium voltage power supply 114 provides amedium voltage source 115 that enables charge circuit 110 and dischargecircuit 108 to ultimately deliver one or more MVT signals to theexterior of the patient. In one embodiment, the medium voltage powersupply is adapted to provide a regulated voltage in the range from20-1000 V.

The defibrillation and MVT stimuli are administered to the patient viapatient interface 116. In one embodiment, patient interface 116 includeselectrodes 118 a and 118 b that are adhesively applied to the patient'schest area, typically with an electrically-conductive gel. Electrodes118 a and 118 b are electrically coupled, such as by insulated copperwire leads 120, to discharge circuit 108. In one example embodiment,electrodes 118 a and 118 b can deliver the defibrillation stimuli andthe MVT stimuli as well as obtain information about the patient'scondition. For example, electrodes 118 can be used to monitor thepatient's cardiac rhythm. Signals originating in the patient that aremeasured by electrodes 118 are fed to monitoring circuitry 122.

In one embodiment, electrodes 118 a and 118 b are part of compoundelectrode patches in which each patch (having a common substrate) has aplurality of individually-selectable electrodes. In this arrangement,device 100 is programmed to select certain ones of the individualelectrodes on each compound patch to achieve a therapeutic purpose. Onesuch purpose is to activate an individual electrode that is mostoptimally placed on the patient's body for the desired MVT ordefibrillation therapy. This approach can be used to correct for thevariability in placement of the electrode patches by unskilled rescuersor even skilled rescuers working under difficult circumstances in thefield. Device 100 in this embodiment may include a switchingarrangement, either electromechanical or electronic, or may communicatecontrol information to an external switching arrangement, which may beincorporated into the compound patch. In a related embodiment, the ECGsignal strength, as measured using various pairs of the individualelectrodes of the compound patches, is used to determine the electrodesto be used for MVT and/or defibrillation administration. In anotherrelated embodiment, the hemodynamic measurement of the MVTeffectiveness, as recorded for different electrode pairs, is used as abasis for switchably selecting the electrodes to be used fordefibrillation. In yet another embodiment, certain electrodes areselected from among the plurality of electrodes on each compound patchto target specific regions to which MVT is to be applied.

In one embodiment, patient interface 116 includes an MVT effectivenesssensor 124 coupled to monitoring circuitry 122. MVT effectiveness sensor124 can measure observable patient characteristics that are related tothe patient's condition, in like fashion to the hemodynamic monitoringand determining arrangements described above for an implantableembodiment. Additional details about the MVT effectiveness monitoringare discussed below.

AED 100 also includes a rescuer interface 126 operatively coupled withcontroller 106. In one embodiment, rescuer interface 126 includes atleast one pushbutton, and a display device for indicating at least theoperational status of AED 100. In a related embodiment, rescuerinterface includes a system for providing visual or audible prompting orinstructions to the rescuer. In another embodiment, rescuer interface126 includes a plurality of human-operable controls for adjusting thevarious AED operational parameters, and a display device that indicatesmeasurements made by monitoring circuitry 122.

FIG. 3B is a diagram illustrating human interface portions of exampleAED 100′ according to one embodiment. AED 100′ is a physicalimplementation of AED 100 (FIG. 1A). AED 100′ is housed in a lightweightportable housing 130 having a base portion 132 and a hinged lid 134 inan exemplary clam-shell arrangement as illustrated, where opening andclosing of the lid turns the device on and off, as diagrammed at 136.Other embodiments do not have the base-cover arrangement, and insteadhave a housing consisting of a single enclosure, in which case thedevice has an on/off switch. The device's relatively small size andweight, and carrying handle 138 facilitate hand-portability of thedevice. Display 126 a′ may have a text only display 140 or may include agraphical display 142 that could, among other items, display an ECGwaveform. The device also has a speaker 126 b for voice prompting of theproper rescue sequence, a non-volatile readiness indicator 126 d′ thatindicates whether or not the device is in working order, an optional“shock” button 126 c′ and receptacles for the patient electrodes 118 a′and 118 b′ and an MVT effectiveness sensor 124′.

AED 100′ includes two types of patient interface. First, electrodes 118a′ and 118 b′ are adapted to be adhesively coupled to the patient'sskin. In one embodiment, the adhesive consists of an electricallyconductive gel. Electrodes 118 a′ and 118 b′ can be used to measure thepatient's cardiac rhythm, and to apply MVT and defibrillation therapy tothe patient. Second, MVT effectiveness sensor 124′ includes a transduceradapted for measuring one or more vital signs of the patient.

FIG. 3C is a diagram of several possible patient 160 connections to anAED 158 according to one embodiment including: defibrillation/ECGelectrodes 118 a′ and 118 b′, pulse oximeter 124 a′, ETCO2 sensor 124b′, Doppler or ultrasound pulse sensor 124 c′, and blood pressure sensor124 d′. More generally, the MVT Effectiveness sensor can be a variant ofany of the monitoring techniques discussed above, for instance, thepulse oximetry measurement for an external embodiment may be achievedusing a fingertip pulse oximeter as the MVT effectiveness sensor 124.Other suitable techniques for monitoring a hemodynamic state of thepatient may also be used. For instance, alternatively or in conjunction:a pulse oximeter, a sonic arterial pulse sensor, a gas sensor, or ablood pressure sensor. In another embodiment, the O₂ saturation sensor124 a′, end tidal sensor 124 b′, and pulse detection unit 124 c′, arebattery-powered and are adapted to communicate measurement data viawireless radio frequency link. For example, BLUETOOTH technology couldbe utilized to accomplish close-range wireless data communications.

In one example embodiment, arterial pulse activity measured from anexterior of the patient by way of pressure sensing, or by way of Dopplerultrasound technology. In one embodiment, the MVT effectiveness sensorincludes a transthoracic impedance measuring arrangement that detectschanges in the chest impedance with cardiac output. Referring again toFIG. 3B, in one embodiment, MVT effectiveness sensor 124′ is integratedwith an adhesive patch adapted to be attached to the patient's skin. Ina related embodiment, the transducer portion of MVT effectiveness sensor124′ is implemented in a thin-or-thick-film semiconductor technology.Examples of suitable sites for arterial pulse sensing include thepatient's aorta, femoral arteries, carotid arteries, and brachialarteries. Other accessible arteries may also be suitable. In one exampleembodiment of AED 100′, the measurement collected via MVT effectivenesssensor 124′ is displayed, substantially in real-time, on display 126′.The displayed measurement can be numerical or graphical, such as abar-type or chart recorder-type display.

In a related embodiment, a plurality of different techniques may be usedtogether in a more advanced AED device enabled with MVT. Such devices,with their multiple sensors to engage with the patient, may be moresuitable for use by trained rescuers, such as paramedics, for example.

In operation, AED 100 is interfaced with the patient via leads 118 a/118b, and MVT effectiveness sensor. In one embodiment, AED 100 providesguidance to a rescuer, via rescuer interface 126, for properlyinterfacing with the patient. AED 100 measures the patient's conditionusing monitoring circuitry 122 and at least a portion of the patientinterface 116. Next, AED 100 analyzes the measured patient's conditionto determine the existence of any indications for treating the patient.If the patient exhibits a condition treatable by AED 100, the devicedetermines the type of therapeutic signal to apply to the patient, andproceeds to apply the treatment. The therapeutic signal can be an MVTsignal, CPR prompt, or a defibrillation signal, either of which isdelivered via discharge circuit 108 and leads 118 a/118 b. During arescue process, AED 100 provides prompting or instructions to a rescuerfor facilitating the therapy and for protecting the rescuer's safety.

Speaking generally for both, implantable, and external MVT-equippedelectrotherapy devices described above, the controllers, i.e.,controller 16, and controller 106, include a processor circuit (e.g.,control unit, arithmetic logic unit, registers, cache, etc.), a datastorage circuit such as volatile or non-volatile memory for storingprogram instructions, input/output facilities, etc. In otherembodiments, the controllers can be implemented as logic circuits suchas field-programmable gate array (FPGA), application-specific integratedcircuit, or the like, or as a combination of the two. In any practicalimplementation, the controller operates according tospecially-configured logic. In microprocessor embodiments, the logic canbe in the form of program instructions which are read and executed. Infixed hardware embodiments, the logic is defined based on theinterconnections of the logic gates.

In various embodiments, a plurality of different MVT waveforms areadapted to force muscular contractions are utilized according toembodiments of the invention. The waveforms are each adapted torepeatedly artificially force and maintain musculature of the patient ina contracted state. Maintaining contraction may or may not be for a timeduration sufficient to achieve myocardial perfusion. Upon cessation ofeach waveform, the targeted musculature relaxes. The time period betweenthe cessation of the MVT and the muscle relaxation varies according tomuscle type, can also vary according to each individual patient's size,physical features, or disease state.

The MVT waveforms discussed herein are administered at a higher energythan a pacing pulse, but at a lower energy than a defibrillation pulse.A pacing pulse is adapted to initiate a myocardial cell activationprocess in the heart, wherein myocardial tissue naturally contracts dueto the heart's natural activation wavefront propagation. Pacing merelyadjusts natural cardiac activity, such as electrically stimulatingcardiac muscles such that they contract synchronously across differentregions of the heart. Therefore, a pacing waveform is incapable ofelectrically forcing and/or maintaining a heart contraction or inducingcardiac perfusion during a cardiac event such as ventricularfibrillation. A defibrillation pulse, on the other hand, involves thedelivery of energy sufficient to shock the heart into a “reset state”,and is intended to reset the natural electrical activity of the heart.In contrast with pacing and defibrillation pulses, in one embodiment,the MVT waveforms as discussed herein are delivered with sufficientenergy to electrically force a cardiac contraction, however withoutdelivering energy intended to perform a cardiac “reset” such as wouldresult from a defibrillation pulse. In various embodiments, the MVTwaveforms discussed herein adapted to artificially force and maintainthe heart or the chest cavity in a contracted state.

FIG. 4A is a diagram illustrating some of the general parameters of theMVT pulse waveforms The train rate TR can be considered to be the forced“heart rate” in beats per minute, since a pulse packet produces onechest constriction. The duration is the length of time for during whicha single session of MVT is applied. FIG. 4B is a diagram detailing asingle pulse packet, having parameters of amplitude (AMP), pulse widthPW, pulse period PP, and train width TW.

Certain effective parameters have been reported in the followingpublished manuscripts, incorporated by reference herein: “TransthoracicApplication Of Electrical Cardiopulmonary Resuscitation For Treatment OfCardiac Arrest,” Crit Care Med, vol. 36, no. 11, pp. s458-66, 2008 and“Coronary Blood Flow Produced by Muscle Contractions Induced byIntracardiac Electrical CPR during Ventricular Fibrillation,” PACE vol.32, pp. S223-7, 2009.

Table 1 below provides an exemplary range of parameter valuescorresponding to empirically determined effectiveness.

TABLE 1 Exemplary Parameter Value Ranges for MVT Value of ParameterValue of Parameter Parameter (Implanted Devices) (External Devices) MVTDuration 20-120 sec. 20-120 sec. Train Rate 30-120 per min. 30-120 permin. Pulse Current 0.25-5 A 0.25-5 A Amplitude Pulse Voltage 15-250 V60-300 V Amplitude Pulse Width 0.15-10 ms 0.15-10 ms Pulse Period 5-70ms 5-70 ms

In one aspect of the invention, the MVT waveform is tuned to increaseselectivity of muscle type in the application of the MVT. Muscle typeselectivity permits more precise targeted forced contractions. In oneparticular embodiment, contractions are separately controlled betweenthe chest musculature (skeletal muscles), and the heart, such that one,the other, or both, may be selectively activated or allowed to relax.

An MVT waveform that is optimized for skeletal muscle capture (OSC)according to one embodiment is adapted to force primarily skeletalmuscle contractions. The OSC waveform is adapted to force a contractionand subsequent release of skeletal muscles in order to vary the pressure(and volume) within the chest cavity. Some amount of ventilation canalso be achieved due to expanding and contracting of the lungs.

An MVT waveform that is optimized for myocardial capture (OMC) accordingto a related embodiment is adapted to force cardiac muscle contractions.The OMC waveform is adapted to force contraction of primarily cardiacmuscles in order to achieve some level of perfusion for the heart andother vital organs. Tables 2 and 3 below provide exemplary ranges forOSC and OMC MVT parameter values; whereas tables 4 and 5 below providean exemplary optimal set of values for OSC and OMC waveforms,respectively.

TABLE 2 Example Ranges of Optimal OSC Parameter Values. VariableParameter Optimal Range Pulsed Output 75-300 V (external); Voltage 20-80V (implantable) Pulsed Output 1-5 A Current Pulse Width .10-.25 ms PulsePeriod 10-20 ms Duration 10-30 seconds Packet Width 100-300 ms TrainRate 80-160 bpm

TABLE 3 Example Ranges of Optimal OMC Parameter Values. VariableParameter Optimal Range Pulsed Output 75-300 V (external); Voltage 20-80V (implantable) Pulsed Output 0.5-5 A Current Pulse Width 5-10 ms PulsePeriod 20-40 ms Duration 10-30 seconds Packet Width 100-300 ms TrainRate 80-160 bpm

TABLE 4 Exemplary Stimulation Waveform for OMC Variable ParameterOptimal Value Pulsed Output 75-300 V (external); Voltage 20-80 V(implantable) Pulsed Output 0.5-1 A Current Pulse Width 7.5 ms PulsePeriod 30 ms Duration 20 seconds Packet Width 200 ms Train Rate 120 bpm

TABLE 5 Exemplary Stimulation Waveform for OSC Variable ParameterOptimal Value Pulsed Output 75-300 V (external); Voltage 20-80 V(implantable) Pulsed Output 2 A Current Pulse Width .15 ms Pulse Period15 ms Duration 20 seconds Packet Width 200 ms Train Rate 120 bpm

In one type of embodiment, the waveform parameters are varied ormodulated for different purposes. One such purpose is to enhance oradjust the MVT effectiveness—that is, to vary the hemodynamic and otherelectrostimulation effects to achieve one or more treatment goals.

One such treatment goal is management of muscle fatigue. MVT stimulationcan, in a matter of a few minutes, fatigue the heart or other muscles toa point where they become un-responsive to further stimulation.Accordingly, in this embodiment, the MVT parameters are set or adjustedto minimize, or simply reduce, MVT-induced muscle fatigue, therebyallowing the MVT treatment to be prolonged.

Another treatment goal is to place the heart into a preferred state inwhich to receive a subsequent defibrillation shock such that thelikelihood of success is improved. According to the MVT is administeredas a series of repeated, time-coordinated, applications of MVT waveformsto optimized for OSC and OMC. The time coordination of these targetedwaveforms permits the chest and heart to be separately placed intorespective states to best receive the defibrillation shock. In one suchapproach, not only is the MVT used for pumping action to maintain thepatient's survival during a life-threatening condition such as VF, butthe parameters of the MVT are specifically adjusted as the time toadminister the defibrillation shock approaches, to improve or optimizethe defibrillation effectiveness.

In one embodiment, as the time to defibrillate approaches, the deviceswitches from an OMC to an OSC waveform for stimulating primarilynon-cardiac muscles. This gives the heart more time to rest, and to bein a “fresher” state for receiving the defibrillation therapy, whichimproves the likelihood of successful conversion of the arrhythmia withdefibrillation.

In another embodiment, a specific timed sequence of OSC and OMCwaveforms is administered. These sequences are specifically designed toestablish separate but synchronized compression cycles in the patient'schest, and myocardium, respectively.

In one approach, the OSC waveform is followed immediately by the OMCwaveform. In a related approach, not only is the muscle capture andcompression effect utilized, but the subsequent release and relaxationof the muscle in response to cessation of an MVT stimulus is used. In aparticular example, the thoracic rebound resulting from cessation of OSCstimulation is a condition to which the defibrillation shock issynchronized.

In a related embodiment, the skeletal muscles are stimulated by OSC, andheart is stimulated by OMC during the later part of the OSC stimulationso that the heart remains compressed while the thoracic musculature isrelaxed. During this period, the defibrillation shock is administered.In this approach, with the cessation of the thoracic musculature, thechest rebounds in an upstroke, and the lungs take in some air. Thisstate tends to concentrate the conductivity, and therefore the currentpath for the defibrillation shock, in the region of the heart. At thesame time, since the heart remains compressed, which also tends toconcentrate the current density of the defibrillation shock in theregion of the heart. In another related embodiment, the OMC isterminated at the same time, or just before, the defibrillation shock.This will tend to relax the myocardium and relieve some of the strainexperienced by the myocardial cells forced into contraction just in timefor the defibrillation shock, but before the heart expands on therebound part of its compression phase.

FIG. 5A is a timing diagram illustrating an example of a synchronized,or time-coordinated, protocol for administering an MVT sequence followedby a time-coordinated defibrillation shock. An OSC waveform 502 isadministrated starting at time T1. In one particular example, The OSC isapplied for 200-300 ms to obtain a full chest compression in view of thedelays from viscosity and mass interactions. A portion of the chestcompression is depicted as curve 506. This is also thought to compressthe right ventricle but not the left ventricle. At time T2, which in oneexample falls within the last 100-150 ms of the OSC waveform, the OMCwaveform 504 is administered. This second MVT waveform 504 issuperimposed on the OSC waveform such that both regions are stimulatedtogether for the overlapping portion. To minimize the effect that theOMC waveform has on the skeletal muscles, its amplitude (i.e. pulsecurrent) is reduced to 10-50% of the current of the OSC. This willresult in a partial contraction of the left ventricle in addition to theright ventricle (thought to also be compressed at this point by thechest compression), but with significantly reduced chest compressioneffect. The secondary compression cycle related to the heart is depictedas curve 510. At time T3, the OSC stimulation is ceased. The chest willrebound in its upstroke phase of the chest compression cycle.

Time T4 is synchronized to coincide with the end portion of the chestrebound. This can be preset in one embodiment as 100 ms. In relatedembodiments, the time period T3-T4 is determined for the particularpatient from one or more previous MVT cycles. In another embodiment, thetime T4 is found in the present cycle based on real-time monitoring ofan indicator of the chest compression state (e.g., impedancemeasurement, pressure measurement, blood flow measurement, etc.),wherein a computation of the time derivative of the monitored indiciacan indicate the end of the upstroke phase of the chest compressioncycle.

At T4, the OMC is ceased, and the defibrillation pulse 508 isadministered. The cessation of the OMC waveform 504 can coincide withthe defibrillation shock, or can precede the defibrillation shock by asmall amount. In this approach, one feature is that the defibrillationshock is timed to strike the heart when the heart is still compressed,even though the OMC administration may have already ended, therebytaking advantage of the increase in the current density which isassociated with this myocardial state. In the embodiment where the OMCis terminated just prior to the defibrillation shock, it is possiblethat the myocardial cells are relieved of their straining, placing themin better condition to respond favorably to the defibrillation energy.

FIG. 5B is a flow diagram illustrating an exemplary process ofadministering the time-coordinated MVT-defibrillation therapy accordingto an embodiment of this type. At 520, the OSC is started. At 522, atime delay is introduced while the pulse packet of the OSC activates andmaintains contraction of the skeletal musculature. At 524, OMC isadministered, and a time delay at 526 is tracked while both types of MVTare simultaneously applied. At 528, the OSC is terminated, causing thechest to begin to relax, during which time 530, the OMC is maintained.At 532, which in one embodiment corresponds approximately to the end ofthe chest's relaxation, or slightly before the end, the OMC isterminated, followed immediately, or very close in time, (e.g., <20 ms)by the defibrillation shock at 534. Following this treatment, thecardiac rhythm is re-assessed to determine whether the defibrillationwas successful.

In one variation of this embodiment, the time delay 530 (i.e., the timebetween T3 and T4 in FIG. 5A) is adjusted so that the cessation of theOMC and defibrillation shock delivery is timed to coincide with adifferent portion of the chest compression rebound. For example, time T4can be targeted to coincide with the middle of the upstroke phase, orwith the beginning of the upstroke phase.

In a related embodiment, in response to an unsuccessful defibrillationattempt, the time delay 530 (i.e., the time between T3 and T4 in FIG.5A) is adjusted to a different part of the chest compression cycle thanin the previous defibrillation attempt. A data structure in thecontroller can maintain a set of values from which to pick, along withan algorithm according to which successive values are selected for thistime delay.

In another type of variation, the defibrillation shock and the OMCcessation are not performed close in time. In fact, the inventorscontemplate that other optimal combinations and timings involvingtime-coordinated OSC stimulation, OMC stimulation, and defibrillation,may be utilized according to future research findings.

In a related embodiment, in devices where nerve stimulation issupported, the MVT is additionally applied to stimulate the phrenicnerve in time-coordinated application with cessation of the OSCstimulation. This can further enhance the chest rebound effect followingthe chest compression caused by the OSC. In one such approach, thephrenic nerve stimulation is started close in time prior to thedefibrillation shock. Thus, the defibrillation is applied at a pointwhere the pressure in the chest cavity is at a minimum value. In anotherapproach, the phrenic nerve stimulation is applied earlier to allowsufficient time for the lungs to expand prior to the defibrillationshock, which may tend to concentrate the defibrillation current path tothe heart region. In a related embodiment, these parameters are variedfrom one defibrillation cycle to another to provide diverse treatmentsin an effort to successfully defibrillate following a failed attempt.

In another related embodiment, the MVT-enabled implantable or externalelectrotherapy device uses its hemodynamic monitoring facilities tomeasure variables such impedance, as blood flow, blood pressure, orblood oxygenation, or a combination thereof, to determine such events asthe phase of the chest or myocardial compression cycles, and MVTeffectiveness. Using this measured information, the intensity andtargeting of the MVT can be adjusted to achieve improved chestcompressions, improved hemodynamic responses from MVT, or improvedmyocardial compressions. In the exemplary embodiment depicted, at 602,the conclusion of an MVT pulse packet is determined. In this window, at604, the chest compression phase is determined based on one or morephysiologic or hemodynamic measurements. At 606, one or more measuresare monitored, recorded, and analyzed, from which adjustments can bemade according to a set of adjustment rules at 608. At 610, at thebeginning of the next pulse train, the determination of the chestcompression phase can be further analyzed.

In varying the MVT waveform to improve its effectiveness according toone type of embodiment, for either the OSC, or OMC waveforms, or inanother type of MVT waveform which may be non-targeted to muscle groups,the pulse period is modulated during administration of the MVTadministration. The degree of modulation can be in the neighborhoods of5%, 10%, 15%, or more. In one variant of this embodiment, the modulationis randomized, or noise-like. In another embodiment, the modulation isapplied with a certain pattern (i.e., with a predetermined modulatingsignal), or with a certain combination of patterns, which can bealternated based on randomization or based on one or more alternationfunctions. Modulation of the pulse period in any of these fashions mayhelp to recruit more muscle fibers than a MVT signal with non-modulatedpulse period, and may reduce or delay the onset of muscle fatigue causedby MVT. Additionally, the modulation of pulse period may enhance thehemodynamic effect, which in turn permits a reduction in pulse amplitudefor an equivalent hemodynamic output or sympathetic stimulation effect.The modulation may also affect the relative timing of the compressioncycle triggered by the MVT.

FIG. 7 is a diagram illustrating an exemplary rescue process that can becarried out by either an implantable device, or an external AED-typedevice. Notably, upon determination of a VF rhythm, at 702, an analysisis made as to whether a defibrillation shock is indicated for theparticular rhythm. If not, then MVT is indicated. This MVT, which isperformed at 704, is adapted for sustaining the life of the patient,i.e., analogous to CPR. The rhythm is re-analyzed subsequent to this MVTtreatment. If defibrillation is indicated, the defibrillation ispreceded by MVT in pre-defibrillation mode along the lines describedabove to place the chest and heart into the best compression cycle stateaccording to the present circumstances and to rules that the device isprogrammed to apply. This pre-treatment MVT is administered at 706, andis followed by a time-coordinated defibrillation shock at 708. In theevent of a failure to defibrillate, the MVT parameters for thepre-defibrillation MVT are adjusted for the next attempt.

In a further aspect of the invention, the various electrodes describedabove for MVT administration can be selectively switched in and out ofthe pulse generating circuitry, enabling selective application of MVT tospecific regions of the body (corresponding to specific muscles ormuscle groups). Table 6 below lists various exemplary muscles that areindividually targeted in one type of embodiment.

TABLE 6 Exemplary Muscles Targeted through Specific MVT ElectrodePlacement Muscle ID Muscle Description A Heart B Right Pectoral C LeftPectoral D Right Intercostals E Left Intercostals F Right Abdominals GLeft Abdominals H Back - left side I Back - right side

In one type of embodiment according to this aspect of the invention, thetargeting of muscles is automatically coordinated and varied based onchanging circumstances, by the MVT-enabled device, to achieve a desiredtherapeutic effect based on the monitored patient condition, includingthe type of arrhythmia, the hemodynamic effect of applied MVT, and onthe specific treatment or rescue algorithm being administered. In arelated embodiment, the targeting of specific muscles is coordinatedwith the MVT waveform to be applied to further enhance the specificityof the MVT targeting.

One example of the desired therapeutic effect is management of musclefatigue. In a corresponding embodiment, certain muscles are stimulatedby MVT for longer or shorter durations based on that muscle's enduranceof MVT. In a related embodiment, muscle groups having left and rightsides, i.e., pectorals, intercostals, abdominals, are stimulated suchthat only one side at a time is activated by MVT, allowing the otherside to rest and recuperate. Variation of muscle selection can bepredetermined according to a programmed algorithm which is selected inresponse to the detected type of arrhythmia. Alternatively, to accountfor variation among patients, selection of muscles for stimulation ismade in response to hemodynamic monitoring.

In one embodiment, the controller of the MVT circuit maintains a one ormore data structures that relate the different muscles for which thedevice is configured to stimulate via MVT, to amplitude and waveformparameter information corresponding to that muscle group. In a relatedembodiment, the data structure(s) further include associations betweentreatment algorithms corresponding to various arrhythmias or patientconditions, as measured by the patient monitoring facilities of thedevice, and MVT parameter values to use for those arrhythmias orconditions.

In one example, the device is programmed to apply relatively higherintensity MVT to one type of muscle group (or one side of the body) thanto another muscle group or side of the body as a test of endurance ofthe patient's musculature to MVT. The other side, which is lessintensely stimulated, may then remain available for longer-duration MVTtherapy.

In a related embodiment, if defibrillation is unsuccessful following thestandard protocol of 4-6 shocks, the MVT for both, the heart and theskeletal muscle, is automatically adjusted to their respectivelow-intensity modes so that the patient's life support can be prolongedwith MVT. This becomes essentially a muscle fatigue management (anddevice energy conservation) strategy.

FIG. 8 is a block diagram of several exemplary logic modules implementedin the controller 800 of an electrotherapy device according to certainembodiments. MVT administration logic controls the various forms of MVTthat can be administered to the patient. High-voltage therapyadministration logic 804 controls the delivery of the defibrillation,which can also have a variable waveform. In one embodiment, HVTadministration logic is further configured to cause the electrotherapycircuitry to administer the HVT based on the relative timing between thereference point and the at least one target point, such that theadministration of the HVT is synchronized with the administration of theMVT based on the relative timing determined by the compression phasedetermining logic, and wherein to achieve that synchronization a timingof the HVT is varied in response to variation of the relative timing.

Arrhythmia detection logic 806 receives input the rhythm monitoringcircuit and provides this information to the MVT and high-voltagetherapy logic modules 802 and 804. Modules 802 and 804 operate toachieve the time-coordinated electrotherapy sequencing discussed abovebased on timing criteria and timing mechanism module 808, which providesinstructions on how to coordinate the various electrotherapy modalities.The timing criteria, being adaptive according to certain embodiments, isadjusted by timing criteria adjustment logic module 812, which in turnreceives inputs from MVT effectiveness determination logic 810, andcompression phase determination logic 814. Each of these modules 810,814 receive input from hemodynamic or physiologic monitoring circuitry,which is itself interfaced with one or more sensors for measuringsuitable indicia such as those discussed above.

Compression phase determination logic, in one embodiment, maintains atleast one data structure that defines various phases of the compressioncycle, and that relates at least one target point in the compressioncycle of the target region to one particular phase of the compressioncycle. This target point may be a point to which the defibrillationshock is synchronized, or referenced to with either some time offset, ordirectly. In another embodiment, the compression phase determinationlogic maintains at least one data structure that associates variousindicia of degree of compression of the target region with variousphases of the compression cycle, and that relates the at least onetarget point in the compression cycle of the target region to oneparticular phase of the compression cycle.

The embodiments above are intended to be illustrative and not limiting.Additional embodiments are within the claims. In addition, althoughaspects of the present invention have been described with reference toparticular embodiments, those skilled in the art will recognize thatchanges can be made in form and detail without departing from the spiritand scope of the invention, as defined by the claims.

Persons of ordinary skill in the relevant arts will recognize that theinvention may comprise fewer features than illustrated in any individualembodiment described above. The embodiments described herein are notmeant to be an exhaustive presentation of the ways in which the variousfeatures of the invention may be combined. Accordingly, the embodimentsare not mutually exclusive combinations of features; rather, theinvention may comprise a combination of different individual featuresselected from different individual embodiments, as understood by personsof ordinary skill in the art.

Any incorporation by reference of documents above is limited such thatno subject matter is incorporated that is contrary to the explicitdisclosure herein. Any incorporation by reference of documents above isfurther limited such that no claims included in the documents areincorporated by reference herein. Any incorporation by reference ofdocuments above is yet further limited such that any definitionsprovided in the documents are not incorporated by reference hereinunless expressly included herein.

For purposes of interpreting the claims for the present invention, it isexpressly intended that the provisions of Section 112, sixth paragraphof 35 U.S.C. are not to be invoked unless the specific terms “means for”or “step for” are recited in a claim.

What is claimed is:
 1. An electrotherapy device for treating arrhythmiain a patient, the device comprising: a patient interface including aplurality of electrodes, each having a surface that facilitateselectrical contact with the patient; electrotherapy circuitryoperatively coupled to the patient interface and including: a mediumvoltage therapy (MVT) circuit operatively coupled to the patientinterface and constructed to administer MVT via the patient interface toeach of a plurality of target regions of the patient, the MVT having aninsufficient energy level to shock the heart into a reset state, buthaving an energy level and a variable waveform that causes musculaturein each corresponding target region to be (a) electrically activatedinto a contracted state, (b) electrically maintained in the contractedstate for a compression duration, and (c) thereafter allowed to relax,thereby achieving a forced compression and release of that targetregion, wherein the plurality of target regions includes a first targetregion having primarily skeletal musculature, and a second target regionhaving primarily myocardial musculature; a high voltage therapy (HVT)circuit operatively coupled to the patient interface and constructed tosupply the HVT via the patient interface, wherein the HVT is of anenergy level sufficient to shock the heart into a reset state; patientmonitoring circuitry including an arrhythmia monitoring circuitoperatively coupled to the patient interface and configured to measureindicia of an arrhythmia treatable by the HVT; and a controller circuitoperatively coupled to the patient monitoring circuitry and theelectrotherapy circuitry, the controller circuit including: MVTadministration logic configured to cause the electrotherapy circuitry toadminister the MVT as a series of repeated, time-coordinated,applications of MVT waveforms to the first and the second targetregions, respectively, in response to a detection of a presence of anarrhythmia treatable by the HVT based on an output of the patientmonitoring circuitry; HVT administration logic configured to cause theelectrotherapy circuitry to administer the HVT in response to thedetection of the presence of the arrhythmia treatable by the HVT, and intime-coordinated response to a sequence of the time-coordinatedapplications of the MVT that includes a first MVT waveform to the firsttarget region and a second MVT waveform to the second target region,such that the HVT is synchronized relative to (a) a first compressioncycle corresponding to activation of the first target region, and (b) asecond compression cycle corresponding to activation of the secondtarget region, resulting from the administration of the MVT.
 2. Theelectrotherapy device of claim 1, wherein the first target regionincludes a portion of the chest of the patient including intercostalmusculature.
 3. The electrotherapy device of claim 1, wherein the HVT isapplied at a target region selected from the plurality of target regionswhich is associated with an increased probability of the effectivenessof the HVT.
 4. The electrotherapy device of claim 1, wherein thesequence of the time-coordinated applications of the MVT includes thefirst MVT waveform, followed immediately by the second MVT waveform. 5.The electrotherapy device of claim 1, wherein the sequence of thetime-coordinated applications of the MVT includes an initiation of thefirst MVT waveform, followed by an initiation of the second MVTwaveform, followed by cessation of the first MVT waveform, followed bycessation of the second MVT waveform, such that the sequence includes afirst portion consisting of application of only the first MVT waveform,a second portion consisting of application of the first MVT waveformsuperimposed with the second MVT waveform, and a third portionconsisting of application of only the second MVT waveform.
 6. Theelectrotherapy device of claim 1, wherein the sequence of thetime-coordinated applications of the MVT includes the first MVTwaveform, followed immediately by the second MVT waveform, wherein thesecond MVT waveform has an amplitude between 10% and 50% of the firstMVT waveform.
 7. The electrotherapy device of claim 1, wherein thesequence of the time-coordinated applications of the MVT includes: thefirst MVT waveform applied for a duration of between 200 and 300 ms; andthe second MVT waveform applied for a duration of between 200 and 250ms, and initiated during the last 100-150 ms of the first MVT waveform.8. The electrotherapy device of claim 1, wherein the HVT is appliedafter cessation of the MVT from the first target region after release ofthe musculature of the first target region occurring in response to thecessation of the MVT activating the first target region.
 9. Theelectrotherapy device of claim 8, wherein the HVT is applied aftercessation of the MVT from the second target region but before release ofthe musculature of the second target region occurring in response to thecessation of the MVT activating the second target region.
 10. Theelectrotherapy device of claim 1, wherein the MVT administration logicis configured to selectively apply the MVT to the first and the secondtarget regions such that activation of the myocardial musculature of thesecond target region is maintained for a certain duration after releaseof the skeletal musculature of the first target region.
 11. Theelectrotherapy device of claim 1, and wherein the MVT administrationlogic is further configured to vary the waveforms of the MVT to vary theselection of a target region subject to MVT administration from amongthe first target region only, the second target region only, and boththe first and the second target regions contemporaneously.
 12. Theelectrotherapy device of claim 1, wherein the controller circuit furtherincludes compression phase determination logic configured to determinerelative timing between a reference point in the administration of theMVT and at least one target point in at least one of the firstcompression cycle and the second compression cycle.
 13. Theelectrotherapy device of claim 12, wherein the HVT administration logicis further configured to cause the electrotherapy circuitry toadminister the HVT based on the relative timing between the referencepoint and the at least one target point, such that the administration ofthe HVT is synchronized with the administration of the MVT based on therelative timing determined by the compression phase determining logic,and wherein to achieve that synchronization a timing of the HVT isvaried in response to variation of the relative timing.
 14. Theelectrotherapy device of claim 12, wherein the compression phasedetermination logic maintains at least one data structure that definesvarious phases of the compression cycle, and that relates the at leastone target point in the compression cycle of the target region to oneparticular phase of the compression cycle.
 15. The electrotherapy deviceof claim 12, wherein the compression phase determination logic maintainsat least one data structure that associates various indicia of degree ofcompression of the target region with various phases of the compressioncycle, and that relates the at least one target point in the compressioncycle of the target region to one particular phase of the compressioncycle.
 16. The electrotherapy device of claim 12, wherein the patientmonitoring circuitry further includes an MVT effectiveness monitoringcircuit operatively coupled to the patient interface and configured todetect indicia of a degree of compression of each respective targetregion activated by the MVT.
 17. The electrotherapy device of claim 16,wherein the compression phase determination logic is configured to causethe MVT effectiveness monitoring circuit to monitor the compression ofthe target region caused by the MVT, and wherein the relative timing isdetermined based on an output of the MVT effectiveness monitoringcircuit.
 18. The electrotherapy device of claim 16, wherein the patientinterface includes at least one hemodynamic sensor, and wherein anoutput of the hemodynamic sensor is coupled to an input of the MVTeffectiveness sensor.
 19. The electrotherapy device of claim 16, whereinthe patient interface includes a pressure sensor configured to measurepressure in the target region, the pressure sensor having sufficientsensitivity to measure a pressure differential between the forcedcompression and the release indicative of a degree of compression of thetarget region caused by the MVT, and wherein an output of the pressuresensor is coupled to an input of the MVT effectiveness sensor.
 20. Theelectrotherapy device of claim 16, wherein the patient interfaceincludes a pulse oximeter sensor configured to measure variation inblood flow in the heart indicative of a degree of compression of thetarget region caused by the MVT, and wherein an output of the pulseoximeter sensor is coupled to an input of the MVT effectiveness sensor.21. The electrotherapy device of claim 16, wherein the MVT effectivenessmonitoring circuit includes an impedance measuring circuit operativelycoupled to the patient interface and configured to measure a change inimpedance across the target region and indicative of a degree ofcompression of the target region caused by the MVT, and wherein anoutput of the impedance monitoring circuit is coupled to an input of theMVT effectiveness sensor.
 22. The electrotherapy device of claim 16,wherein the controller circuit further includes: MVT effectivenessassessment logic configured to assess a strength of muscle contractioncaused by the MVT based on a computation of a rate of change of theoutput of the MVT effectiveness monitoring circuit.
 23. Theelectrotherapy device of claim 16, wherein the MVT circuit isconstructed to produce a waveform defined by series of pulse trainscomposed of pulses having an adjustable set of parameters including: anadjustable pulse width, an adjustable pulse period, and an adjustablepulse amplitude; and wherein the MVT administration logic is configuredto vary the adjustable set of parameters based on an output of the MVTeffectiveness monitoring circuit such that the degree of compression ofa target region selected for MVT administration caused by the MVT isincreased.
 24. The electrotherapy device of claim 1, wherein theplurality of electrodes includes nerve stimulation electrodesconstructed to be placed in electrical communication with the phrenicnerve of the patient, and wherein the MVT circuit includes a portionoperatively coupled with the nerve stimulation electrodes; and whereinthe MVT administration logic is configured to cause the MVT circuit tostimulate the phrenic nerve during release of the musculature of thefirst target region in response to cessation of the MVT activating thefirst target region.
 25. The electrotherapy device of claim 1, whereinthe compression duration is sufficient to achieve myocardial perfusion.26. The electrotherapy device of claim 1, wherein the plurality ofelectrodes includes electrodes positioned at various regions of thetorso of the patient, and wherein the electrotherapy circuitry isadapted to selectively apply the first MVT waveform to specific one ormore regions via selected groupings of the plurality of electrodes suchthat various different muscle groups of skeletal musculature areselectively targeted by the MVT.
 27. The electrotherapy device of claim1, wherein the MVT circuit is constructed such that a pulse current ofthe MVT delivered to the patient falls within the range of 0.25 and 5amperes.
 28. The electrotherapy device of claim 1, wherein the HVTadministration logic includes a HVT retry procedure configured to causethe electrotherapy circuitry to administer a subsequent HVT in responseto a failure of a preceding HVT administration to convert thearrhythmia; and wherein the HVT administration logic further includes asynchronization adjustment procedure configured to cause theelectrotherapy circuitry to administer the subsequent HVT such that thesubsequent HVT is synchronized to a different point in at least one ofthe first compression cycle and the second compression cycle than thepreceding HVT.